1. Field of the Invention
This invention relates to highly stable emulsified compositions showing a high degree of water and moisture retention.
2. Description of the Prior Art
Conventional emulsified compositions used as cosmetics (such as emulsified lotions and skin creams) and external preparations for the skin (such as emulsions and ointments) are principally those of the oil-in-water type, prepared by emulsifying, in water, an oily base such as oil and fat, hydrocarbons (e.g., liquid paraffin and ceresin), animal and vegetable oil (e.g., olive oil and beef tallow), and higher fatty acids.
In these compositions, nonionic surfactants of the Span or Tween series are employed to ensure a stable emulsified condition.
The surface-active agents of this type, however, are not preferable as ingredients of cosmetics or external preparations because of their irritative action to the skin and in terms of their feel upon application.
Elastin is a kind of hard protein found in connective tissues of mammalians (particularly in the nuchal ligament and in the middle layer of aortas) together with collagen. Pure elastin isolated from these materials, or soluble elastin obtained by hydrolysis of these materials with an enzyme, has been used in cosmetics and other products as an ingredient to impart the property of water and moisture retention.
Recently, it was found that an elastin hydrolyzate having a molecular weight of 10,000 to 100,000 shows a high effect to stabilize emulsions, and emulsified compositions for cosmetic use containing the same together with a higher alcohol, surface-active agent and others were disclosed (Japanese Patent Kokai No. 59-231007).
The cosmetics using the above-mentioned elastin hydrolyzate having a molecular weight of 10,000 to 100,000 are still insufficient in emulsion stability, requiring further addition of an emulsifier (e.g., surface-active agent) for practical use. In addition, the water and moisture retention is also insufficient, and hence some other humectants need be added. Thus, the problem of disagreeable skin feeling, such as sticky touch, remains unresolved.